1. Field of Invention
The present invention relates to a chemical-mechanical polishing (CMP) device. More particularly, the present invention relates to a slurry distributor.
2. Description of Related Art
In semiconductor manufacturing, surface planarization is a major step before conducting any high-density photolithographic processes. To transfer conductive line pattern in a photo-exposure operation accurately, light dispersion must be minimized as much as possible. The only way to reduce dispersion is to remove as much surface roughness from the surface of a wafer as possible.
The most common techniques for planarizing wafer surface include spin-on-glass (SOG) and chemical-mechanical polishing (CMP). However, as semiconductor manufacturing progresses into the sub-half-micron line width range, spin-on-glass no longer can attain the level of surface planarity desired. Consequently, chemical-mechanical polishing has almost become the sole means for providing the level of planarity required to manufacture very large scale integration (VLSI) and ultra large scale integration (ULSI) chips. Since chemical-mechanical polishing is an anisotropic polishing process, the process is able not only to planarize a wafer surface globally but also to fabricate vertical and horizontal interconnects of a damascene structure. In addition, CMP can also be applied to fabricate shallow trench isolation structures or other advanced devices, planarize micro-electromechanical systems and manufacture flat display panels.
In general, chemical-mechanical polishing utilizes mechanical abrasion to remove surface material. To conduct a wafer polishing operation, the polishing table and the wafer carrier of a chemical-mechanical polishing system each rotates in fixed direction. The wafer carrier grips the backside of a wafer and presses the front surface of the wafer against a polishing pad on the polishing table. In the meantime, slurry is continuously supplied to the polishing pad. When bumps on the surface of the wafer contact the polishing pad, chemical agents within the slurry will react with bump material while abrasive particles within the slurry enhance mechanical abrasion so that the bumps are gradually removed. Continuous application of the chemical reaction and mechanical abrasion ultimately produces a highly planar surface. If various polishing factors are properly controlled, a chemical-mechanical polishing operation may produce a surface planarity up to 94% or higher.
In chemical-mechanical polishing, the quality of slurry has a leading role in the stability of the process. Since slurry is normally concentrated for ease of packaging, the slurry must be diluted by using a solvent before actual use on the polishing table. Because the rate of chemical reaction depends on the chemical agents inside the slurry and the polishing condition depends on the state of abrasive particles, different type of slurry is used to polish different material surface. Typically, two or more types of slurry are used singly or alternatively in a surface planarization operation.
A conventional chemical-mechanical polishing system has a mixer for mixing up chemical ingredient in-situ so that two or more types of slurry are supplied to the polishing pad when required. However, due to brief mixing of chemical ingredients in an in-situ process, quality of the slurry often varies. Furthermore, slurry is distributed to various locations on the polishing pad during a chemical-mechanical polishing operation. Hence, the slurry is not distributed uniformly over the entire surface of the polishing pad. Since a non-uniform distribution of slurry may affect the polishing rate and polishing uniformity of the wafer surface, quality and performance of the polishing operation is very much compromised.
A conventional slurry distributor is disclosed in U.S. Pat. No. 5,921,849. FIG. 1A is a top view of the conventional slurry distributor. FIG. 1B is a side view of the conventional slurry distributor and FIG. 1C is a cross-sectional view along line I-Ixe2x80x2 of the conventional distributor as shown in FIG. 1A.
As shown in FIGS. 1A to 1C, the slurry distributor 100 has a truncated conical shape. The distributor 100 includes a base section 102 and a main body section 104. A groove 106 is formed in the interior of the main body section 104. The groove 106 mainly serves as a slurry accumulator and a reservoir for mixing up the slurry ingredients before distribution. The main body section 104 also has six rectangular pipelines 108. Each pipeline 108 is formed on the upper edge of the groove 106. All pipelines 108 are in connection with the groove 106 so that the accumulated slurry within the groove 106 may flow to the polishing pad via the pipelines 108. In addition, the base section 102 of the slurry distributor 100 has a concave opening 110 for connecting to a lapping wheel (not shown) on the chemical-mechanical polishing table.
To use the slurry distributor 100 in a chemical-mechanical polishing operation, both the slurry distributor 100 and the lapping wheel rotate around an axle. Two or more types of slurry are fed to the distributor 100 and mixed within the groove 106 due to axial rotation of the distributor 100. The mixed slurry flows out of the groove 106 through the pipelines 108 and drops to the polishing pad surface from the edge of the main body 104.
However, the aforementioned chemical-mechanical polishing system has at least the following drawbacks. When different types of slurry are fed to the groove 106 of the distributor 100, some of the slurry may splash over leading to unwanted pollution of surrounding sensors. Ultimately, these sensors may lose their wafer monitoring function causing a drop in wafer yield. Furthermore, if the slurry is not completely flushed away by incoming solvent, some of the abrasive particles may accumulate inside the groove 106 and produce non-uniformly mixed slurry. The inability to supply uniformly mixed slurry to each wafer carrier of a multi-head polishing device renders the slurry distributor unsuitable for providing slurry to the polishing pad of a multi-head polishing system. In addition, if the slurry supply pipelines converge upon a point slightly off center from the center of the slurry distributor 100, different polishing head may receive a slightly different version of the slurry. Consequently, uniform polishing of each wafer is impossible.
Accordingly, one object of the present invention is to provide a slurry distributor for mixing up different types of slurry and distributing the well-mixed slurry evenly over a polishing pad.
A second object of this invention is to provide a slurry distributor capable of preventing inappropriate out-splashing that may pollute surrounding devices.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a slurry distributor. The distributor comprises a base section, a main body section, a distributing structure (a sidewall section) and a connecting structure. The distributing structure (the sidewall section) mounts on top of the main body section for accommodating one or more types of slurry, mixing up the different types of slurry and permitting the well-mixed slurry to flow out evenly. The distributing structure also includes a plurality of holes near the main body section. The connecting structure is formed within the base section for linking up with a chemical-mechanical polishing device.
The slurry distributor according to this invention has a distributing structure (sidewall section). The distributing structure is able to prevent any out-splashing of slurry to pollute surround devices. Furthermore, the distributing structure may also serve as a buffer controlling the rate of dropping of slurry. In addition, an arch-shaped surface is formed at the lower section of the distributing structure so that abrasive particles suspended within the slurry will not accumulate inside the slurry distributor. Hence, different types of slurry are uniformly mixed to form homogenous slurry with stable quality.
The distributing structure of the slurry distributor further includes a plurality of holes near the main body section so that the distributor rotates around a spin axle. The slurry flows out through these holes and spreads out evenly on the polishing pad. Consequently, the slurry distributor of this invention can be used to delivery slurry evenly over a polishing pad having a multi-head system.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.